U.S. patent application number 12/419367 was filed with the patent office on 2009-07-30 for gas supply system, substrate processing apparatus and gas supply method.
This patent application is currently assigned to TOKYO ELECTRON LIMITED. Invention is credited to Kenetsu MIZUSAWA.
Application Number | 20090191337 12/419367 |
Document ID | / |
Family ID | 38223147 |
Filed Date | 2009-07-30 |
United States Patent
Application |
20090191337 |
Kind Code |
A1 |
MIZUSAWA; Kenetsu |
July 30, 2009 |
GAS SUPPLY SYSTEM, SUBSTRATE PROCESSING APPARATUS AND GAS SUPPLY
METHOD
Abstract
Prior to wafer processing, pressure ratio control is executed on
a divided flow rate adjustment means so as to adjust the flow rates
of divided flows to achieve a target pressure ratio with regard to
the pressures in the individual branch passages. As the processing
gas from a processing gas supply means is diverted into first and
second branch pipings under the pressure ratio control and the
pressures in the branch passages then stabilize, the control on the
divided flow rate adjustment means is switched to steady pressure
control for adjusting the flow rates of the divided flows so as to
hold the pressure in the first branch passage at the level achieved
in the stable pressure condition. Only after the control is
switched to the steady pressure control, an additional gas is
delivered into the second branch passage via an additional gas
supply means.
Inventors: |
MIZUSAWA; Kenetsu;
(Yamanashi, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
TOKYO ELECTRON LIMITED
Tokyo
JP
|
Family ID: |
38223147 |
Appl. No.: |
12/419367 |
Filed: |
April 7, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11615062 |
Dec 22, 2006 |
|
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12419367 |
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60773676 |
Feb 16, 2006 |
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Current U.S.
Class: |
427/248.1 ;
137/13 |
Current CPC
Class: |
H01J 37/32449 20130101;
Y10T 137/0391 20150401; H01J 37/3244 20130101; C23C 16/45557
20130101; C23C 16/45561 20130101; C23C 16/5096 20130101 |
Class at
Publication: |
427/248.1 ;
137/13 |
International
Class: |
C23C 16/00 20060101
C23C016/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 4, 2006 |
JP |
2006-000241 |
Claims
1. A gas supply method adopted in conjunction with a gas supply
system that supplies gases into a processing chamber where a
substrate is processed, wherein: said gas supply system comprises:
a processing gas supply means for supplying a processing gas to be
used to process the substrate; a processing gas supply passage
through which the processing gas from said processing gas supply
means flows; a first branch passage and a second branch passage
branching from the processing gas supply passage and connected to
said processing chamber at different positions; a divided flow rate
adjustment means for adjusting the divided flow rates of the
processing gas diverted into said branch passages from said
processing gas supply passage based upon pressures in said branch
passage; an additional gas supply means for supplying an additional
gas; and an additional gas supply passage through which the
additional gas from said additional gas supply means is made to
flow into said second branch passage at a position further
downstream relative to said divided flow rate adjustment means; and
said gas supply method comprises: a step executed before processing
the substrate in which the processing gas is supplied via said
processing gas supply means and pressure ratio control is executed
on said divided flow rate adjustment means to adjust the divided
flow rates so as to achieve a target pressure ratio for the
pressures in said branch passages; and a step executed once the
pressures in said branch passages become stabilized through
pressure ratio control in which the additional gas is supplied via
the additional gas supply means after switching the control on said
divided flow rate adjustment means to steady pressure control for
adjusting the divided flow rates so as to hold the pressure in said
first branch passage at a level achieved in stable pressure
conditions.
2. The gas supply method according to claim 1, further comprising:
a step in which once the pressures inside said branch passages
stabilize after starting the additional gas supply, the control on
said divided flow rate adjustment means is switched to pressure
ratio control for adjusting the flow rates of the divided flows so
as to achieve a new target pressure ratio matching the pressure
ratio of the pressures in said branch passages measured in the
stable pressure conditions.
3. The gas supply method according to claim 1, wherein: said
divided flow rate adjustment means includes valves each used to
adjust the flow rate of the processing gas flowing through one of
said branch passages and pressure sensors each used to measure the
pressure in one of said branch passages; and said divided flow rate
adjustment means adjusts the flow rate ratio of the flows of the
processing gas from said processing gas supply passage by adjusting
the degrees of openness of said valves based upon the pressures
detected with said pressure sensors.
4. The gas supply method according to claim 1, wherein: said
processing gas supply means includes a plurality of gas supply
sources and supplies into said processing gas supply passage the
processing gas constituted with a mixed gas achieved by mixing
gases from said gas supply sources delivered at specific flow
rates.
5. The gas supply method according to claim 1, wherein: said
additional gas supply means includes a plurality of gas supply
sources and supplies into said additional gas supply passage the
additional gas constituted with a mixed gas containing selected
gases among the gases from said gas supply sources or containing
gases delivered from said gas supply sources with a predetermined
gas flow rate ratio.
6. The gas supply method according to claim 1, wherein: said first
branch passage is disposed so that the processing gas flowing
through said first branch passage is supplied toward a central area
on a surface of said substrate in said processing chamber; and said
second branch passage is disposed so that the processing gas
flowing through said second branch passage is supplied toward a
peripheral area on the surface of said substrate.
7. The gas supply method according to claim 1, wherein: said second
branch passage is made up of a plurality of branch passages
branching from said processing gas supply passage so that the
additional gas from said additional gas supply means is delivered
into the plurality of second branch passages.
8. A substrate processing method performed using a gas supply
system that supplies gases into a processing chamber where a
substrate is processed, the gas supply system including a
processing gas supply means for supplying a processing gas to be
used to process the substrate, a processing gas supply passage
through which the processing gas from said processing gas supply
means flows, a first branch passage and a second branch passage
branching from the processing gas supply passage and connected to
said processing chamber at different positions, a divided flow rate
adjustment means for adjusting the divided flow rates of the
processing gas diverted into said branch passages from said
processing gas supply passage based upon pressures in said branch
passage, an additional gas supply means for supplying an additional
gas, and an additional gas supply passage through which the
additional gas from said additional gas supply means is made to
flow into said second branch passage at a position further
downstream relative to said divided flow rate adjustment means,
said method comprising: supplying, before processing the substrate,
the processing gas using said processing gas supply means;
controlling said divided flow rate adjustment means to adjust the
divided flow rates so as to achieve a target pressure ratio for the
pressures in said branch passages; and supplying, once the
pressures in said branch passages become stabilized through the
controlling step, additional gas via the additional gas supply
means, the pressures in said branch passages becoming stabilized
after controlling said divided flow rate adjustment means to adjust
the divided flow rates such that the pressure in said first branch
passage is held at a level achieved in stable pressure
conditions.
9. The substrate processing method according to claim 8, further
comprising: controlling, once the pressures inside said branch
passages stabilize after starting the additional gas supply, the
divided flow rate adjustment means to adjust the flow rates of the
divided flows so as to achieve a new target pressure ratio matching
the pressure ratio of the pressures in said branch passages
measured in the stable pressure conditions.
10. The substrate processing method according to claim 8, wherein:
said divided flow rate adjustment means includes valves each used
to adjust the flow rate of the processing gas flowing through one
of said branch passages and pressure sensors each used to measure
the pressure in one of said branch passages; and said divided flow
rate adjustment means adjusts the flow rate ratio of the flows of
the processing gas from said processing gas supply passage by
adjusting the degrees of openness of said valves based upon the
pressures detected with said pressure sensors.
11. The substrate processing method according to claim 8, wherein:
said processing gas supply means includes a plurality of gas supply
sources and supplies into said processing gas supply passage the
processing gas constituted with a mixed gas achieved by mixing
gases from said gas supply sources delivered at specific flow
rates.
12. The substrate processing method according to claim 8, wherein:
said additional gas supply means includes a plurality of gas supply
sources and supplies into said additional gas supply passage the
additional gas constituted with a mixed gas containing selected
gases among the gases from said gas supply sources or containing
gases delivered from said gas supply sources with a predetermined
gas flow rate ratio.
13. The substrate processing method according to claim 8, wherein:
said first branch passage is disposed so that the processing gas
flowing through said first branch passage is supplied toward a
central area on a surface of said substrate in said processing
chamber; and said second branch passage is disposed so that the
processing gas flowing through said second branch passage is
supplied toward a peripheral area on the surface of said
substrate.
14. The substrate processing method according to claim 8, wherein:
said second branch passage is made up of a plurality of branch
passages branching from said processing gas supply passage so that
the additional gas from said additional gas supply means is
delivered into the plurality of second branch passages.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional Application of, and claims
the benefit of priority under 35 U.S.C. .sctn. 120 from, U.S.
application Ser. No. 11/615,062, filed Dec. 22, 2006 and U.S.
Provisional Application No. 60/773,676, filed Feb. 16, 2006 which
claims the benefit of priority under 35 U.S.C. .sctn. 119 from
Japanese Patent Application Number 2006-000241, filed on Jan. 4,
2006. The entire contents of each of the above applications are
incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a gas supply system that
supplies gas into a processing chamber, a substrate processing
apparatus and a gas supply method.
BACKGROUND OF THE INVENTION
[0003] In a substrate processing apparatus used in fields of
application pertaining to the present invention, a specific type of
processing such as film formation or etching is executed on a
target substrate to undergo processing (hereafter simply referred
to as a substrate), which may be a semiconductor wafer or a liquid
crystal substrate, by using a specific gas supplied into a
processing chamber.
[0004] Such a substrate processing apparatus may be, for instance,
a plasma processing apparatus. The plasma processing apparatus may
include a lower electrode also used as a stage on which a substrate
is placed and an upper electrode also used as a showerhead through
which the gas is injected toward the substrate, both disposed
within the processing chamber. In a plane parallel plate type
plasma processing apparatus such as this, plasma is generated by
applying high-frequency power to the space between the two
electrodes while supplying the specific gas onto the substrate
placed inside the processing chamber through the showerhead and the
specific type of processing such as film formation or etching is
executed with the plasma thus generated.
[0005] It has been a matter of crucial importance in the related
art to improve the planar uniformity achieved through the specific
substrate processing, such as film formation or etching executed on
the substrate by assuring consistent substrate surface processing
characteristics such as the etching rate, etching selection ratio,
the film formation rate or the like.
[0006] Japanese Laid Open Patent Publication No. H08-158072 (patent
reference literatures 1) and Japanese Laid Open Patent Publication
No. H09-045624 (patent reference literatures 2), for instance,
address this need by proposing that the space within the showerhead
be partitioned into a plurality of gas chambers, that gas supply
pipings be connected to the individual gas chambers independently
of one another and that a processing gas of a given type or at a
given flow rate be supplied to each of a plurality of areas within
the substrate surface. The art disclosed in patent reference
literatures 1 and 2 makes it possible to improve the planar
uniformity achieved through a substrate etching process by
adjusting the gas concentration at the substrate surface in units
of the individual local areas.
[0007] The gases used in the actual substrate processing include a
plurality of types of gases such as a processing gas that directly
affects the substrate processing, a gas used to control deposition
of reaction products resulting from the substrate processing and a
carrier gas such as an inert gas selected in a specific combination
so as to best suit the material on the substrate undergoing the
processing or the specific processing conditions. For this reason,
a mass flow controller must be installed for purposes of flow rate
control in correspondence to each of the gas supply pipings
connected to the individual gas chambers in the showerhead, as
disclosed in patent reference literature 2.
[0008] However, such a structure in the related art, which includes
a gas supply system in correspondence to the gas to be supplied
from each gas chamber even if the gases used for different purposes
may contain a common gas constituent, necessitates flow rate
control to be executed separately for the gas supplied from each
gas chamber. This is bound to result in a complex piping structure
and require complex flow rate control for the individual pipings,
necessitating, for instance, a large piping space and leading to a
significant increase in the control onus.
[0009] In addition, even if the gases can be supplied through
simple control from a plurality of areas within the processing
chamber, the desired level of planar uniformity must be assured by
ensuring that the control does not allow any fluctuation of the
flow rate ratio (divided flow ratio) of the processing gases
supplied from the various positions that may occur due to, for
instance, a fluctuation of the pressures with which the gases are
drawn in. In other words, the gas supply must be controlled without
being affected by pressure fluctuations or the like.
SUMMARY OF THE INVENTION
[0010] Accordingly, an object of the present invention, which has
been completed by addressing the problems discussed above, is to
provide a gas supply system with a simple piping structure and the
like, with which the desired level of planar uniformity is achieved
by supplying the gases from a plurality of positions within the
processing chamber under simple control.
[0011] The object described above is achieved in an aspect of the
present invention by providing a gas supply system that supplies
gases into a processing chamber where a substrate undergoing
processing is processed, comprising a processing gas supply means
for supplying a processing gas to be used to process the substrate,
a processing gas supply passage through which the processing gas
from the processing gas supply means flows, a first branch passage
and a second branch passage branching from the processing gas
supply passage and connected to the processing chamber at different
positions, a divided flow rate adjustment means for adjusting the
divided flow rates of the processing gas diverted into the
individual branch passages from the processing gas supply passage
based upon the pressures within the branch passages, an additional
gas supply means for supplying an additional gas, an additional gas
supply passage through which the additional gas from the additional
gas supply means is made to flow into the second branch passage at
a position further downstream relative to the divided flow rate
adjustment means and a control means for supplying the processing
gas via the processing gas supply means and executing pressure
ratio control on the divided flow rate adjustment means to adjust
the divided flow rates so as to achieve a target pressure ratio for
the pressures within the individual branch passages before
processing the substrate and for supplying the additional gas via
the additional gas supply means after switching the control on the
divided flow rate adjustment means to steady pressure control
through which the divided flow rates are adjusted so as to hold the
pressure in the first branch passage at a level achieved in stable
pressure conditions once the pressures in the individual branch
passages become stabilized.
[0012] The object described above is achieved in another aspect of
the present invention by providing a substrate processing apparatus
comprising a processing chamber where a substrate is processed, a
gas supply system that supplies gases into the processing chamber
and a control means for controlling the gas supply system. The gas
supply system in the substrate processing apparatus comprises a
processing gas supply means for supplying a processing gas to be
used to process the substrate, a processing gas supply passage
through which the processing gas from the processing gas supply
means flows, a first branch passage and a second branch passage
branching from the processing gas supply passage and connected to
the processing chamber at different positions, a divided flow rate
adjustment means for adjusting the divided flow rates of the
processing gas diverted into the individual branch passages from
the processing gas supply passage based upon the pressures within
the branch passages, an additional gas supply means for supplying
an additional gas and an additional gas supply passage through
which the additional gas from the additional gas supply means is
made to flow into the second branch passage at a position further
downstream relative to the divided flow rate adjustment means. The
control means supplies the processing gas via the processing gas
supply means and executes pressure ratio control on the divided
flow rate adjustment means to adjust the divided flow rates so as
to achieve a target pressure ratio for the pressures within the
individual branch passages before processing the substrate and
supplies the additional gas via the additional gas supply means
after switching the control on the divided flow rate adjustment
means to steady pressure control through which the divided flow
rates are adjusted so as to hold the pressure in the first branch
passage at a level achieved in stable pressure conditions once the
pressures in the individual branch passages become stabilized.
[0013] The object described above is also achieved in yet another
aspect of the present invention by providing a gas supply method to
be adopted in conjunction with a gas supply system that supplies
gases into a processing chamber where a substrate is processed. The
gas supply system comprises a processing gas supply means for
supplying a processing gas to be used to process the substrate, a
processing gas supply passage through which the processing gas from
the processing gas supply means flows, a first branch passage and a
second branch passage branching from the processing gas supply
passage and connected to the processing chamber at different
positions, a divided flow rate adjustment means for adjusting the
divided flow rates of the processing gas diverted into the
individual branch passages from the processing gas supply passage
based upon the pressures within the branch passages, an additional
gas supply means for supplying an additional gas and an additional
gas supply passage through which the additional gas from the
additional gas supply means is made to flow into the second branch
passage at a position further downstream relative to the divided
flow rate adjustment means. The gas supply method includes a step
executed before processing the substrate, in which the processing
gas is supplied via the processing gas supply means and pressure
ratio control is executed on the divided flow rate adjustment means
to adjust the divided flow rates so as to achieve a target pressure
ratio for the pressures inside the individual branch passages and a
step executed once the pressures within the branch passages become
stabilized through the pressure ratio control in which the
additional gas is supplied via the additional gas supply means
after switching the control on the divided flow rate adjustment
means to steady pressure control for adjusting the divided flow
rates so as to hold the pressure in the first branch passage at a
level achieved in stable pressure conditions.
[0014] According to the present invention described above, the
processing gas from the processing gas supply means is diverted
into the first and second branch passages, the processing gas
originating from the processing gas supply means is directly
supplied into the processing chamber through the first branch
passage and the processing gas, the gas composition and flow rate
of which are adjusted by adding the additional gas, is supplied
into the processing chamber through the second branch passage. This
means that a gas constituent common in the processing gases flowing
through the individual branch passages is supplied from the common
processing gas supply means whereas the gas composition and the
flow rate of the processing gas flowing through the second branch
passage are adjusted by adding the additional gas as necessary.
Since the structure requires the minimum number of pipings and thus
simplifies the piping structure, the flow rate control, too, can be
simplified.
[0015] In addition, since the divided flow control on the divided
flow rate adjustment means is switched from the pressure ratio
control to the steady pressure control before supplying the
additional gas, the processing gas that should flow into the second
branch passage is not allowed to flow into the first branch passage
even if the pressure inside the second branch passage fluctuates
when the additional gas is supplied into the second branch passage.
As a result, a specific flow rate ratio (divided flow ratio) is
sustained for the flows of the processing gas diverted into the
individual branch passages even as the additional gas is supplied,
allowing the processing gas, the flow of which is divided at a
desired flow rate ratio to be delivered to different areas of the
substrate surface. Thus, the desired level of planar uniformity can
be achieved.
[0016] Once the pressures within the individual branch passages
become stabilized after starting the additional gas supply, the
control means may designate the pressure ratio of the pressures in
the branch passages detected in the stable pressure conditions as a
new target pressure ratio and may switch the control on the divided
flow rate adjustment means to pressure ratio control for adjusting
the divided flow rates so as to match the pressure ratio of the
pressures in the branch passages with the new target pressure
ratio. By reverting the control on the divided flow rate adjustment
means from the steady pressure control to the pressure ratio
control as described above, the pressure ratio of the pressures
within the individual branch passages can be held unchanged through
the pressure ratio control, since the pressures in the branch
passages also fluctuate if the conductance at the gas supply holes
changes and the pressure ratio is thus controlled to remain
unchanged. In other words, even if the conductance at the gas
supply holes changes over time, the flow rate ratio of the flows of
the processing gas diverted into the individual branch passages can
be held steady at the target level.
[0017] In addition, the divided flow rate adjustment means may
include valves each used to adjust the flow rate of the processing
gas flowing through one of the branch passages and pressure sensors
each used to measure the pressure within one of the branch
passages. Such a divided flow rate adjustment means is capable of
adjusting the flow rate ratio of the flows of the processing gas
originating from the processing gas supply passage by adjusting the
degrees of openness of the valves based upon the pressures detected
with the individual pressure sensors.
[0018] The processing gas supply means may include a plurality of
gas supply sources and may supply into the processing gas supply
passage the processing gas constituted with a mixed gas achieved by
mixing gases from the individual gas supply sources delivered at
specific flow rates. In addition, the additional gas supply means
may include a plurality of gas supply sources and may supply into
the additional gas supply passage the additional gas constituted
with a mixed gas containing selected gases among the gases from the
various gas supply sources or containing gases delivered from the
gas supply sources and mixed at a predetermined gas flow rate
ratio. In this structure, the processing gas constituted with a
mixed gas containing a plurality of common gas constituents to be
delivered into both branch passages, is supplied from the
processing gas supply means and the additional gas is added as
necessary to the processing gas flowing through the second branch
passage so as to adjust its gas composition or its flow rate. As a
result, a further reduction is achieved in the number of pipings
required in the structure, resulting in an even simpler piping
structure.
[0019] Furthermore, the first branch passage may be disposed so
that the processing gas flowing through the passage is supplied
toward a central area on the substrate surface in the processing
chamber and the second branch passage may be disposed so that the
processing gas flowing through the passage is supplied toward a
peripheral area of the substrate surface. By adopting this
positional arrangement, a further improvement can be achieved in
the processing uniformity over the central area and the peripheral
area of the substrate.
[0020] The second branch passage may be made up of a plurality of
branch passages branching from the processing gas supply passage so
that the additional gas from the additional gas supply means can be
delivered into the plurality of second branch passages. In this
case, the processing gas can be delivered to each of a plurality of
areas in the periphery of the substrate, which enables even finer
control for achieving processing uniformity at the peripheral area
of the substrate.
[0021] The present invention provides a gas supply system assuming
a simple piping structure and the like with which a gas can be
supplied from a plurality of positions within the processing
chamber under simple control the desired level of planar uniformity
can be assured.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a sectional view of an example of a structure that
may be adopted in a substrate processing apparatus achieved in an
embodiment of the present invention;
[0023] FIG. 2 is a block diagram showing an example of a structure
that may be adopted in the control unit in FIG. 1;
[0024] FIG. 3 is a block diagram showing an example of a structure
that may be adopted in the gas supply system in the embodiment;
[0025] FIG. 4 presents a flowchart of an example of processing that
may be executed in the substrate processing apparatus in the
embodiment; and
[0026] FIG. 5 presents a flowchart of another example of processing
that may be executed in the substrate processing apparatus in the
embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0027] The following is a detailed explanation of the preferred
embodiment of the present invention, given in reference to the
attached drawings. It is to be noted that in the specification and
the drawings, the same reference numerals are assigned to
components with substantially identical functions and structural
features so as to eliminate the need for a repeated explanation
thereof.
(Structural Example for Substrate Processing Apparatus)
[0028] First, the substrate processing apparatus achieved in the
embodiment of the present invention is explained in reference to a
drawing. FIG. 1 is a sectional view schematically showing the
structure adopted in the substrate processing apparatus in the
embodiment. The substrate processing apparatus in the figure is a
plain parallel plate-type plasma etching apparatus.
[0029] The substrate processing apparatus 100 includes a processing
chamber 110 constituted with a substantially cylindrical processing
container. The processing container, which may be constituted of,
for instance, an aluminum alloy, is electrically grounded. In
addition, the inner wall surfaces of the processing container are
coated with an alumina film or an yttrium oxide film.
[0030] Inside the processing chamber 110, a susceptor 116
constituting a lower electrode also to function as a stage, on
which a wafer W, i.e., a substrate to undergo processing, is
placed, is disposed. More specifically, the susceptor 116 is
supported on a susceptor support base 114 assuming the shape of a
circular column, which is disposed at a substantial center at the
bottom via an insulating plate 112 within the processing chamber
110. The susceptor 116 may be constituted of, for instance, an
aluminum alloy.
[0031] Over the susceptor 116, an electrostatic chuck 118, which
holds the wafer W, is disposed. The electrostatic chuck 118
includes an internal electrode 120. A DC power source 122 is
electrically connected to the electrode 120. The wafer W can be
attracted and pulled onto the upper surface of the electromagnetic
chuck 118 through the coulomb force generated as a DC voltage is
applied to the electrode 120 from the DC power source 122.
[0032] In addition, a focus ring 124 is disposed at the upper
surface of the susceptor 116 so as to enclose the periphery of the
electrostatic chuck 118. It is to be noted that a cylindrical inner
wall member 126 constituted of, for instance, quartz, is attached
to the outer circumferential surfaces of the susceptor 116 and the
susceptor support base 114.
[0033] A coolant space 128 assuming a ring shape is formed inside
the susceptor support base 114. The coolant space 128 is made to
communicate with a chiller unit (not shown), which may be
installed, for instance, outside the processing chamber 110, via
pipings 130a and 130b. The coolant (a liquid coolant or cooling
water) is supplied via the pipings 130a and 130b so that the
coolant circulates through the coolant space 128. The temperature
of the wafer W placed on the susceptor 116 is thus controlled.
[0034] A gas supply line 132 passing through the susceptor 116 and
the susceptor support base 114 is connected to the upper surface of
the electrostatic chuck 118. A heat transfer gas (backside gas)
such as He gas can be delivered to the area between the wafer W and
the electrostatic chuck 118 via this gas supply line 132.
[0035] Above the susceptor 116, an upper electrode 134 is disposed
so as to range parallel to and face opposite the susceptor 116
constituting the lower electrode. A plasma generation space PS is
formed between the susceptor 116 and the upper electrode 134.
[0036] The upper electrode 134 includes an inner upper electrode
138 assuming a disc shape and an outer upper electrode 136 assuming
a ring shape and encircling the inner upper electrode 138 from the
outside. A dielectric member 142 assuming a ring shape is disposed
between the outer upper electrode 136 and the inner upper electrode
138. An insulating shield 144 assuming a ring shape, which may be
constituted of, for instance, alumina, is fitted with a high level
of airtightness between the outer upper electrode 136 and the inner
circumferential wall of the processing chamber 110.
[0037] A first high-frequency power source 154 is electrically
connected to the outer upper electrode 136 via a feeder tube 152, a
connector 150, an upper feeder rod 148 and a matching unit 146. A
high frequency voltage with a minimum frequency of 40 MHz (e.g., 60
MHz) can be output from the first high-frequency power source
154.
[0038] The lower end of the feeder tube 152, which may assume a
substantially cylindrical shape with an open bottom, is connected
to the outer upper electrode 136. The lower end of the upper feeder
rod 148 is electrically connected via the connector 150 to the
center of the upper surface of the feeder tube 152. The upper end
of the upper feeder rod 148 is connected to the output side of the
matching unit 146. The matching unit 146, connected to the first
high-frequency power source 154, matches the internal impedance at
the first high-frequency power source with a load impedance.
[0039] The exterior of the feeder tube 152 is covered with a
cylindrical grounded conductor 111 which includes a circular side
wall with a diameter substantially equal to the diameter of the
processing chamber 110. The lower end of the grounded conductor 111
is connected to the top of the side wall of the processing chamber
110. The upper feeder rod 148 mentioned earlier passes through the
central area of the upper surface of the grounded conductor 111,
with an insulating member 156 disposed over the area where the
grounded conductor 111 and the upper feeder rod 148 contact each
other.
[0040] The inner upper electrode 138 constitutes a showerhead
through which a specific gas is delivered onto the wafer W placed
on the susceptor 116. The inner upper electrode 138 includes a
round electrode plate 160 having formed therein numerous gas supply
holes 160a and an electrode support member 162 that detachably
supports the upper surface side of the electrode plate 160. The
electrode support member 162 assumes the shape of a disc with a
diameter substantially equal to the diameter of the electrode plate
160.
[0041] A buffer space 163 constituted with a cylindrical space is
formed inside the electrode support member 162. An annular barrier
member 164 is installed inside the buffer space 163 and the buffer
space 163 is divided by the annular barrier member 164 into an
inner first buffer space 163a constituted with a cylindrical space
and an outer second buffer space 163b constituted with a
ring-shaped space surrounding the first buffer space 163a. This
annular barrier member 164 may be constituted with, for instance,
an O-ring.
[0042] The first buffer space 163a is formed so as to face opposite
the central area (the central portion) of the wafer W placed on the
susceptor 116, whereas the second buffer space 163b is formed so as
to face opposite the peripheral area (edge portion) of the wafer W
surrounding the central area.
[0043] The gas supply holes 160a communicate with the lower surface
ranging over the buffer spaces 163a and 163b. Thus, a specific gas
can be injected toward the central portion of the wafer W via the
first buffer space 163a, whereas the specific gas can be injected
toward the edge portion of the wafer W via the second buffer space
163b. The specific gas is supplied via a gas supply system 200 into
the individual buffer spaces 163a and 163b.
[0044] A lower feeder tube 170 is electrically connected to the
upper surface of the electrode support member 162, as shown in FIG.
1. The lower feeder tube 170 is connected to the upper feeder rod
148 via the connector 150. A variable capacitor 172 is installed in
the lower feeder tube 170. Through adjustment of the electrostatic
capacity of the variable capacitor 172, the relative ratio of the
intensity of the electrical field formed directly under the outer
upper electrode 136 and the intensity of the electrical field
formed directly under the inner upper electrode 138 as the high
frequency voltage from the first high-frequency power source 154 is
applied can be adjusted.
[0045] An exhaust port 174 is formed at the bottom of the
processing chamber 110. The exhaust port 174 is connected via an
exhaust pipe 176 to an exhaust device 178 which includes a vacuum
pump and the like. As the processing chamber 110 is evacuated with
the exhaust device 178, the pressure within the processing chamber
110 can be lowered so as to achieve a desired degree of vacuum.
[0046] A second high-frequency power source 182 is electrically
connected to the susceptor 116 via a matching unit 180. A high
frequency voltage in a range of 2 to 20 MHz, e.g., a high frequency
voltage with a frequency of 2 MHz, can be output from the second
high-frequency power source 182.
[0047] A low pass filter 184 is electrically connected to the inner
upper electrode 138 constituting part of the upper electrode 134.
The low pass filter 184 is installed so as to block the
high-frequency from the first high-frequency power source 154 and
pass the high-frequency from the second high-frequency power source
182 to the ground. A high pass filter 186 is electrically connected
to the susceptor 116 constituting the lower electrode. The high
pass filter 186 is installed so as to pass the high-frequency from
the first high-frequency power source 154 to the ground.
(Gas Supply System)
[0048] Next, the gas supply system 200 is explained in reference to
drawings. In the example presented in FIG. 1, the processing gas is
divided into two flows, i.e., a first processing gas (processing
gas for the center portion) to be delivered toward the central
portion of the wafer W inside the processing chamber 110 and a
second processing gas (processing gas for the edge portion) to be
delivered toward the edge portion of the wafer W. It is to be noted
that instead of dividing the processing gas into two separate flows
as in the embodiment, the processing gas may be divided into three
or more separate flows.
[0049] As shown in FIG. 1, the gas supply system 200 comprises a
processing gas supply means 210 for supplying a processing gas to
be used to execute a specific type of processing on the wafer W,
such as film formation or etching, and an additional gas supply
means 220 for supplying a specific type of additional gas. The
processing gas supply means 210 is connected with a processing gas
supply piping 202 constituting a processing gas supply passage, and
a first branch piping 204 to constitute a first branch passage and
a second branch piping 206 to constitute a second branch passage
both branch out from the processing gas supply piping 202. It is to
be noted that the first and second branch pipings 204 and 206 may
branch out inside a divided flow rate adjustment means 230 or they
may branch outside the divided flow rate adjustment means 230.
[0050] The first and second branch pipings 204 and 206 are
connected to the upper electrode 134 in the processing chamber 110
at different positions, e.g., to the first and second buffer spaces
163a and 163b in the inner upper electrode 138.
[0051] The gas supply system 200 further includes the divided flow
rate adjustment means (e.g., a flow splitter) 230 for adjusting the
flow rates of the divided processing gas flows, i.e., the first
processing gas and the second processing gas, through the first and
second branch pipings 204 and 206 based upon the pressures detected
within the first and second branch pipings 204 and 206. In
addition, the additional gas supply means 220 is connected to the
second branch piping 206 at a middle position therein via an
additional gas supply piping 208 at a position further downstream
relative to the divided flow rate adjustment means 230.
[0052] In the gas supply system 200 adopting the structure
described above, the processing gas originating from the processing
gas supply means 210 is diverted into the first branch piping 204
and the second branch piping 206 with the divided flow rates
adjusted by the divided flow rate adjustment means 230. The first
processing gas flowing through the first branch piping 204 is
delivered toward the central portion of the wafer W via the first
buffer space 163a, whereas the second processing gas flowing
through the second branch piping 206 is delivered toward the edge
portion of the wafer W via the second buffer space 163b.
[0053] After the additional gas is supplied from the additional gas
supply means 220 in this gas supply system, the additional gas
flows through the additional gas supply piping 208 into the second
branch piping 206 where it is mixed with the second processing gas.
Then, the additional gas, mixed with the second processing gas is
delivered toward the edge portion of the wafer W via the second
buffer space 163b. It is to be noted that a specific example of a
structure that may be adopted in the gas supply system 200 is to be
described in detail later.
[0054] A control unit 300, which controls the various units of the
substrate processing apparatus 100, is connected to the substrate
processing apparatus 100. The control unit 300 controls the DC
power source 122, the first high-frequency power source 154, the
second high-frequency power source 182 and the like as well as the
processing gas supply means 210, the additional gas supply means
220, the divided flow rate adjustment means 230 and the like in the
gas supply system 200.
(Structural Example for Control Unit)
[0055] An example of a structure that may be adopted in the control
unit 300 is now explained in reference to a drawing. FIG. 2 is a
block diagram showing an example of a structure that may be adopted
in the control unit 300. As shown in FIG. 2, the control unit 300
comprises a CPU (central processing unit) 310 constituting the
control unit main body, a RAM (random access memory) 320 that
includes a memory area to be used by the CPU 310 when it executes
various types of data processing, a display means 330 constituted
with a liquid crystal display or the like at which an operation
screen, a selection screen and the like are displayed, an operation
means 340 constituted with, for instance, a touch panel through
which the operator is able to input and edit various types of data
such as process recipes and various types of data including process
recipes and process logs can be output into a specific storage
medium, a storage means 350 and an interface 360.
[0056] Processing programs that enable the execution of various
types of processing in the substrate processing apparatus 100,
information (data) needed for the execution of the processing
programs and the like are stored in the storage means 350. The
storage means 350 may be constituted with a memory, a hard disk
(HDD) or the like. The CPU 310 reads out program data and the like
as required to execute the processing programs for specific types
of processing. For instance, the CPU 310 executes gas supply
processing by controlling the gas supply system 200 so as to supply
the specific gas into the processing chamber 110 before the wafer W
is processed.
[0057] The various units controlled by the CPU 310, such as the
divided flow rate adjustment means 230, the processing gas supply
means 210 and the additional gas supply means 220, are connected to
the interface 360. The interface 360 may be constituted with, for
instance, a plurality of I/O ports.
[0058] The RAM 320, the display means 330, the operation means 340,
the storage means 350, the interface 360 and the like are connected
with the CPU 310 via a bus line such as a control bus or a data
bus.
(Structural Example for Gas Supply System)
[0059] Next, specific structural examples that may be adopted in
the individual units constituting the gas supply system 200 are
explained. FIG. 3 is a block diagram presenting a specific
structural example for the gas supply system 200. The processing
gas supply means 210 may be constituted with a gas box housing
therein a plurality of (e.g., three) gas supply sources 212a, 212b
and 212c, as shown in FIG. 3. The pipings for the individual gas
supply sources 212a to 212c are connected to the processing gas
supply piping 202 where the individual gas constituents from the
different gas supply sources flow as a mixed gas. At the piping
corresponding to each of the gas supply sources 212a to 212c, one
of mass flow controllers 214a to 214c is installed in order to
adjust the flow rate of the specific gas constituent. The gas
constituents from the individual gas supply sources 212a to 212c
are thus mixed so as to achieve a predetermined flow rate ratio at
the processing gas supply means 210 adopting the structure
described above, and the mixed gas, which then flows out into the
processing gas supply piping 202, is diverted into the first and
second branch pipings 204 and 206.
[0060] The gas supply source 212a is filled with a C.sub.xF.sub.y
gas, constituted with a fluorocarbon fluorine compound such as
CF.sub.4, C.sub.4F.sub.6, C.sub.4F.sub.8 or C.sub.5F.sub.8, to be
used as, for instance, an etching gas, as shown in FIG. 3. The gas
supply source 212b is filled with O.sub.2 gas, for instance, to be
used to control the deposition of, for instance, CF reaction
products. The gas supply source 212c is filled with rare gas such
as an Ar gas to be used as a carrier gas. It is to be noted that
the number of gas supply sources at the processing gas supply means
210 is not limited to that in the example shown in FIG. 3, and
there may be a single gas supply source, two gas supply sources or
four or more gas supply sources in the processing gas supply means
210.
[0061] The additional gas supply means 220 may be constituted with
a gas box housing therein a plurality of (e.g., two) gas supply
sources 222a and 222b, as shown in FIG. 3. The pipings for the
individual gas supply sources 222a and 222b are connected to the
additional gas supply piping 208 where the individual gas
constituents from the different gas supply sources flow as a mixed
gas. At the piping corresponding to each of the gas supply sources
222a and 222b, one of mass flow controllers 224a and 224b is
installed in order to adjust the flow rate of the specific gas
constituent. The gas from either of the gas supply sources 222a and
222b is selected or the gases from the gas supply sources 222a and
222b are mixed at a predetermined gas flow rate ratio at the
additional gas supply means 220 adopting the structure described
above, and the additional gas from the additional gas supply means,
which then flows out into the additional gas supply piping 208, is
delivered into the second branch piping 206 located further
downstream of the divided flow rate adjustment means 230.
[0062] The gas supply source 222a is filled with a C.sub.xF.sub.y
gas, with which an etching process, for instance, can be speeded
up, whereas the gas supply source 222b is filled with a O.sub.2 gas
with which the deposition of, for instance, CF reaction products
can be controlled. It is to be noted that the number of gas supply
sources in the additional gas supply means 220 is not limited to
that in the example presented in FIG. 3, and a single gas supply
source or three or more gas supply sources may be housed in the
additional gas supply means.
[0063] The divided flow rate adjustment means 230 includes a
pressure adjustment unit 232 which adjusts the pressure inside the
first branch piping 204 and a pressure adjustment unit 234 that
adjusts the pressure inside the second branch piping 206. More
specifically, the pressure adjustment unit 232 comprises a pressure
sensor 232a that detects the pressure inside the first branch
piping 204 and a valve 232b via which the degree of openness of the
first branch piping 204 is adjusted, whereas the pressure
adjustment unit 234 comprises a pressure sensor 234a that detects
the pressure inside the second branch piping 206 and a valve 234b
via which the degree of openness of the second branch piping 206 is
adjusted.
[0064] The pressure adjustment units 232 and 234 are connected to a
pressure controller 240 which, in response to a command issued by
the control unit 300, adjusts the degrees of openness of the valves
232b and 234b based upon the pressures detected with the pressure
sensors 232a and 234a respectively. The control unit 300 may
control the divided flow rate adjustment means 230 through, for
instance, pressure ratio control. In such a case, the pressure
controller 240 adjusts the degrees of openness of the valves 232b
and 234b so that the flow rates of the first and second processing
gases achieve a target flow rate ratio indicated in the command
from the control unit 300, i.e., so that the pressures inside the
first and second branch pipings 204 and 206 achieve a target
pressure ratio. It is to be noted that the pressure controller 240
may be a control board built into the divided flow rate adjustment
means 230, or it may be provided in a separate frame from the
divided flow rate adjustment means 230. As a further alternative,
the pressure controller 240 may be installed within the control
unit 300.
[0065] Before the processing on the wafer W, such as etching, a
specific gas is supplied into the processing chamber 110 via the
gas supply system 200 in the substrate processing apparatus 100.
More specifically, the processing gas is first supplied from the
processing gas supply means 210 and pressure ratio control is
executed for the divided flow rate adjustment means 230. Then, once
the pressure ratio of the pressures inside the first and second
branch pipings 204 and 206 is adjusted to the target pressure
ratio, the additional gas from the additional gas supply means 220
is delivered into the second branch piping 206.
[0066] The following problem is bound to occur if the additional
gas is delivered into the second branch piping 206 while the
divided flow rate adjustment means 230 remains under the pressure
ratio control. Namely, as the additional gas is delivered into the
second branch piping 206, the pressure inside the second branch
piping 206 will rise to a level higher than the pressure inside the
first branch piping 204, thereby altering the pressure ratio, and
accordingly, the divided flow rate adjustment means 230 will
automatically adjust the degrees of openness of the valves 232b and
234b so as to sustain the target pressure ratio. As a result, the
first processing gas will flow in greater quantity than the second
processing gas, causing the flow rate ratio of the flow rates of
the first and second processing gases to become destabilized due to
the additional gas supply.
[0067] This problem may be addressed by fixing the degrees of
openness of the valves 232b and 234b in the divided flow rate
adjustment means 230 once the pressure ratio of the pressures
inside the first and second branch pipings 204 and 206 becomes
equal to the target pressure ratio and the pressures inside the
individual pipes become stabilized and then by supplying the
additional gas, so as to disallow automatic engagement of the
valves 232b and 234b when the additional gas is supplied and to
hold the flow rate ratio of the first and second processing gases
unchanged.
[0068] However, since the pressure inside the second branch piping
206 increases as the additional gas is supplied, the processing gas
will be diverted toward the second branch piping 206 less readily
and and more processing gas will be allowed to flow into the first
branch piping 204 if the settings at the valves 232b and 234b in
the divided flow rate adjustment means 230 are fixed as described
above. In other words, even if the settings at the valves 232b and
234b in the divided flow rate adjustment means 230 are fixed, the
flow rate ratio of the flow rates of the first and second
processing gases will be destabilized as the additional gas is
supplied.
[0069] Accordingly, the divided flow control in the divided flow
rate adjustment means 230 is switched from the pressure ratio
control under which the pressures inside the first and second
branch pipings 204 and 206 are controlled so as to sustain the
target pressure ratio, to steady pressure control, under which the
pressure inside the first branch piping 204 is held at a steady
level, before the additional gas supply starts in the gas supply
processing according to the present invention. Once the divided
flow control is switched, the additional gas supply is started.
[0070] By adopting these measures, it is ensured that the pressure
inside the first branch piping 204 is held at a steady level even
as the additional gas is supplied and, as a result, even if the
pressure inside the second branch piping 206 fluctuates, the
processing gas that should be diverted into the second branch
piping 206 is not allowed to flow into the first branch piping 204.
Thus, the flow rate ratio of the first and second processing gases
does not become unstable due to the additional gas supply.
(Example of Gas Supply Processing)
[0071] Now, a specific example of the gas supply processing
executed in the embodiment of the present invention described above
is explained. FIG. 4 presents a flowchart of a specific example of
processing that may be executed in the substrate processing
apparatus, which includes the gas supply processing according to
the present invention. First, the control unit 300 starts supplying
the processing gas via the processing gas supply means 210 in step
S110. A predetermined type of gas within the processing gas supply
means 210 thus flows into the processing gas supply piping 202 at a
predetermined flow rate. More specifically, the C.sub.xF.sub.y gas,
the O.sub.2 gas and the Ar gas supplied from the gas supply sources
212a to 212c at predetermined flow rates become mixed, thereby
forming a mixed gas containing the C.sub.xF.sub.y gas, the O.sub.2
gas and the Ar gas with a predetermined mixing ratio. This mixed
gas constituting the processing gas then flows into the processing
gas supply piping 202.
[0072] Then, in step S120, the control unit 300 executes the
pressure ratio control for the divided flow rate adjustment means
230, under which the divided flow rate adjustment means 230 adjusts
the flow rates of the divided flows of the processing gas. More
specifically, in response to a pressure ratio control command
issued by the control unit 300, the divided flow rate adjustment
means 230 adjusts the degrees of openness of the valves 232b and
234b based upon the pressures measured by the pressure sensors 232a
and 234a under the control executed by the pressure controller 240,
until the pressure ratio of the pressures inside the first and
second branch pipings 204 and 206 becomes equal to the target
pressure ratio. The flow rate ratio of the first and second
processing gases to be delivered into the first and second buffer
spaces 163a and 163b via the first and second branch pipings 204
and 206 is thus determined.
[0073] Then, in step S130, a decision is made as to whether or not
the pressures in the first and second branch pipings 204 and 206
have stabilized. If it is decided that the pressures have
stabilized, the control unit 300 executes the steady pressure
control for the divided flow rate adjustment means 230 in step
S140, under which the divided flow rate adjustment means 230
adjusts the flow rates of the divided flows of the processing
gas.
[0074] Namely, in response to a steady pressure control command
issued by the control unit 300, the divided flow rate adjustment
means 230 adjusts the degrees of openness of the valves 232b and
234b based upon the pressures measured by the pressure sensors 232a
and 234a under the control executed by the pressure controller 240,
so as to hold steady the pressure of the first processing gas
flowing through the first branch piping 204. It is to be noted that
the mixed gas (with which the same etching process can be executed)
with the same gas composition as that of the mixed gas delivered
into the first buffer space 163a, at least, will also have been
delivered into the second buffer space 163b at this point in
time.
[0075] In step S1 50, the control unit 300 starts supplying the
additional gas via the additional gas supply means 220. The
predetermined type of additional gas is thus delivered at a
predetermined flow rate from the additional gas supply means 220
into the second branch piping 206 via the additional gas supply
piping 208.
[0076] In this example, a C.sub.xF.sub.y gas (e.g., CF.sub.4 gas)
with which the etching process can be accelerated is supplied at
the predetermined flow rate from the gas supply source 222a via the
additional gas supply means 220 and the gas delivered from the
additional gas supply means is then diverted into the second branch
piping 206 to be supplied into the second buffer space 163b via the
second branch piping 206. As a result, a processing gas with a
higher CF.sub.4 content compared to the processing gas delivered
into the first buffer space 163a is supplied into the second buffer
space 163b. The gas composition and the flow rate of the processing
gas to be delivered into the second buffer space 163b are
determined in this manner.
[0077] Then, in step S160, a decision is made as to whether or not
the pressures inside the first and second branch pipings 204 and
206 have both stabilized. If it is decided in step S160 that the
pressures have become stable, the processing of the wafer W is
executed in step S200. Through the gas supply processing described
above, the mixed gas flowing through the first buffer space 163a is
delivered over the space near the center of the wafer W placed on
the susceptor 116 and the mixed gas with a higher CF.sub.4 gas
concentration flowing through the second buffer space 163b is
delivered to the space over the periphery of the wafer W under
depressurized conditions in the substrate processing apparatus 100.
As a result, the etching characteristics at the periphery of the
wafer W can be adjusted relative to the etching characteristics at
the central area of the wafer W, which makes it possible to assure
uniform planar etching characteristics at the wafer W.
[0078] Through the processing in the flowchart presented in FIG. 4
explained above, the processing gas from the processing gas supply
means 210 is diverted into the first and second branch pipings 204
and 206, the processing gas from the processing gas supply means
210 is directly delivered into the processing chamber 110 via the
first branch piping 204, and a specific type of additional gases
added into the processing gas flowing through the second branch
piping 206 so as to deliver the processing gas into the processing
chamber 110 after adjusting its gas composition and flow rate.
Thus, the processing gas constituted of common gas constituents to
flow through both the branch pipings 204 and 206 is supplied from
the processing gas supply means 210, and the additional gas is
added into the processing gas flowing through the second branch
piping 206 as necessary so as to adjust its gas composition or flow
rate. This means that when the processing gas is flowing through
the individual branch pipings have a large number of common gas
constituents, the optimal processing gas supply can be achieved
with fewer pipes than that required in a structure that includes
processing gas sources installed in correspondence to the
individual branch pipings. Since the number of pipes in the gas
supply system 200 is thus minimized, the piping structure in the
gas supply system 200 is further simplified. In addition, since the
flow rates of the divided flows of the processing gas are adjusted
based upon the pressures inside the individual branch pipings 204
and 206, the processing gas can be supplied through a plurality of
positions within the processing chamber 110 without requiring
complex control.
[0079] Furthermore, by simply switching the control on the divided
flow rate adjustment means 230 from the pressure ratio control to
the steady pressure control prior to the start of the additional
gas supply, it is ensured that the divided flow rate adjustment
means 230 adjusts the valves 232b and 234b so as to hold the
pressure in the first branch piping 204 at a steady level under the
steady pressure control even if the pressure ratio of the pressures
in the first and second branch pipings 204 and 206 fluctuates as
the additional gas supply starts. As a result, the processing gas
that should flow into the second branch piping 206 is not even
partially allowed to flow into the first branch piping 204. Since
the flow rate ratio of the first and second processing gases from
the divided flow rate adjustment means 230 does not fluctuate as
the additional gas supply starts as described above, the desired
level of planar uniformity is assured.
[0080] It is to be noted that while an explanation is given in
reference to FIG. 4 on an example in which the wafer is processed
by sustaining the steady pressure control for the divided flow rate
adjustment means 230 selected in step S140, the control on the
divided flow rate adjustment means 230 may revert to the pressure
ratio control prior to the wafer processing.
[0081] For instance, the conductance at the gas supply holes 160a
may change due to a gradual increase in the temperature at the
upper electrode 134 while processing a single wafer or while
continuously processing a plurality of wafers, and in such a case,
the gas may no longer flow smoothly.
[0082] Under such circumstances, the pressures within the first and
second branch pipings 204 and 206 will both rise and thus, if the
steady pressure control for the divided flow rate adjustment means
230 is sustained, the valves 232b and 234b will be adjusted so as
to hold the pressure in the first branch piping 204 alone at a
steady level. As a result, the ratio of the second processing gas
flowing into the second branch piping 206 will gradually increase
relative to the ratio of the first processing gas flowing into the
first branch piping 204, resulting in destabilization of the flow
rate ratio of the first and second processing gases.
[0083] This phenomenon may be prevented by reverting to the
pressure ratio control prior to the wafer processing. Namely, by
reverting to the pressure ratio control, it is ensured that the
pressures within the first and second branch pipings 204 and 206
will both fluctuate and the pressure ratio will remain unchanged
even when the conductance at the gas supply holes 160a changes. In
other words, the divided flow rate adjustment means can be
controlled so as to ensure that the pressure ratio of the pressures
within the first and second branch pipings 204 and 206 remains
unchanged. By adopting these measures, it is thus ensured that any
change in the conductance at the gas supply holes 160a occurring
over time will not alter the flow rate ratio of the first and
second processing gases.
[0084] More specifically, additional processing may be executed in
steps S170 and S180 prior to the processing in step S200, as shown
in FIG. 5. Namely, in the flowchart presented in FIG. 5, the
control on the divided flow rate adjustment means 230 is switched
to the pressure ratio control by the control unit 300 in step S170
if it is decided in step S160 that the pressures in the first and
second branch pipings 204 and 206 have stabilized. In more specific
terms, the pressure ratio is of the pressures inside the first and
second branch pipings 204 and 206 measured when the pressures have
stabilized is designated as a new target pressure ratio and the
control on the divided flow rate adjustment means 230 is switched
to pressure ratio control for adjusting the flow rates for the
divided flows so as to achieve the new target pressure ratio with
the pressures in the first and second branch pipings 204 and 206.
In the processing, the pressure ratio of the pressures inside the
first and second branch pipings 204 and 206 measured in stable
pressure conditions is designated as the new target pressure ratio
for the following reasons; as the additional gas is being delivered
into the second branch piping 206, the additional gas in the second
branch pipe alters the pressure inside the second branch piping 206
and accordingly, the fluctuation of the pressure attributable to
the additional gas delivered into the second branch piping is taken
into consideration in the pressure ratio control so as to enable
the divided flow rate adjustment means 230 to adjust the flow rates
of the divided flows without affecting the flow rate ratio of the
first and second processing gases.
[0085] Then, in step S180, a decision is made as to whether or not
the pressures inside the first and second branch pipings 204 and
206 have both stabilized. If it is decided in step S180 that the
pressures have become stable, the processing of the wafer W is
executed in step S200.
[0086] Through the processing in FIG. 5 explained above, the wafer
can be processed while preventing fluctuation of the flow rate
ratio of the first and second processing gases even if the
conductance at the gas supply holes 160a at the upper electrode 134
changes while executing the wafer processing.
[0087] It is to be noted that the second branch piping 206 in the
embodiment may be made up of a plurality of branch pipings
branching from the processing gas supply piping 202 so that the
additional gas from the additional gas supply means 220 can be
delivered into the plurality of second branch pipings. In this
case, the processing gas can be delivered to each of a plurality of
areas in the periphery of the wafer, which enables even finer
control for achieving processing uniformity at the peripheral area
of the wafer.
[0088] In addition, while an explanation is given above in
reference to the embodiment on an example in which the processing
gas supplied from the gas supply system 200 is injected toward the
wafer W through the top of the processing chamber 110, the present
invention is not limited to this example and it may be adopted in
conjunction with a structure in which the processing gas is also
delivered through another portion of the processing chamber 110
such as the side surface of the processing chamber 110 facing the
plasma generation space PS. Since this will allow the specific type
of processing gas to be delivered from above and the side of the
plasma generation space PS, adjustment of the gas concentration
within the plasma generation space PS will be enabled, which, in
turn, further improves the planar uniformity of the wafer being
processed.
[0089] While the invention has been particularly shown and
described with respect to the preferred embodiment thereof by
referring to the attached drawings, the present invention is not
limited to this example and it will be understood by those skilled
in the art that various changes in form and detail may be made
therein without departing from the spirit, scope and teaching of
the invention.
[0090] For instance, while an explanation is given above in
reference to the embodiment on an example in which the flow rates
of the divided flow of the processing gas diverted into the branch
pipings are adjusted via the pressure adjustment units, the present
invention is not limited to this example and the flow rates of the
divided flows of the processing gas diverted into the branch
pipings may instead be adjusted by using mass flow controllers. In
addition, while an explanation is given above in reference to the
embodiment on an example in which the present invention is adopted
in a plasma etching apparatus used to process substrates, the
present invention may also be adopted in other types of substrate
processing apparatuses to which processing gases are supplied,
e.g., film forming apparatuses such as a plasma CVD apparatus, a
sputtering apparatus and a thermal oxidation apparatus.
Furthermore, the present invention may be adopted in substrate
processing apparatuses in which substrates other than wafers, such
as FPDs (flat panel displays) and mask reticles for photomasks, are
processed or MEMS (micro-electro mechanical system) manufacturing
apparatuses, as well.
* * * * *